A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
The temperature stability of some components in a lithographic apparatus and components associated with a lithographic apparatus, as well as some objects which enter a lithographic apparatus, is important. Typically such components are maintained at a target set-point temperature. There are many different thermal loads originating in and around a lithographic apparatus which can cause the temperature of components to rise above or fall below their target set-point temperature. Therefore thermal shields are used in a lithographic apparatus for thermally insulating components from a thermal load.
One use of a thermal shield is in a system which is configured to handle a substrate. For example a thermal shield can be used in a system which receives a substrate, ensures the temperature stability of the substrate, and provides the substrate to a lithographic apparatus. Additionally, after imaging of the substrate in the lithographic apparatus, the system can receive the substrate from the lithographic apparatus and pass it on for further processing. The temperature stability of a substrate is important because temperature instabilities in the substrate can lead to imaging errors, such as overlay errors. Therefore, a space in the system through which the substrate passes is thermally shielded with the thermal shield for thermally insulating the space from a thermal load originating outside the space.
A thermal shield comprising an insulating material is known. However, the effectiveness of such a thermal shield is dependent on the low thermal conductivity and thickness of the insulating material. In a lithographic apparatus space is at a premium and a thermal shield with good enough thermal insulating performance made only of an insulating material is undesirably bulky.
A thermal shield comprising a wall thermally conditioned with a flowing liquid (e.g. a water jacket) has good thermal shielding properties and takes up less volume than a thermal shield made only of insulating material. However, a wall thermally conditioned with liquid has the disadvantages of increased complexity due to the necessity to make liquid tight seals and the risk of damage to the apparatus due to liquid leaks.
It is an aim of the present invention to provide a system for use with a lithographic apparatus, wherein the system is configured to handle a substrate and thermally insulate a space through which the substrate passes from at thermal load originating outside the space.